The space in lavatories of aircraft and the like is severely restricted, so lavatories are required to be as compact as possible. Therefore, doors are folding doors that do not require a large space in which to move. The folding doors mounted on these lavatories have a mechanism that automatically closes an open door in order to ensure safety and to block unpleasant odors (see Japanese Unexamined Patent Application Publication No. H7-11836).
The folding door of Japanese Unexamined Patent Application Publication No. H7-11836 uses coil springs in a door closing mechanism that automatically closes open doors. Conventionally, door closing mechanisms that automatically close open doors, such as the invention of Japanese Unexamined Patent Application Publication No. H7-11836, use coil springs as so-called torsion springs. As such, when opening or closing the door, stress accumulates around regions where helical wound wires formed at top and bottom ends of the coil springs is stretched straight, and thus the top and bottom ends of the coil springs are easily damaged, which has been a cause of reduced durability. Furthermore, there is a demand for a door opening and closing device that can be more easily attached and removed from the door panels.